In recent years, the resolver of a rotating electric machine (i.e., a motor) has been gradually replaced by a rotation position detector. Within a rotation position detector, the magneto-resistive element of a magnetic sensor detects a rotation position of a rotor core. For example, a patent document 1 (i.e., Japanese Patent Laid-Open No. 2012-152091) discloses a rotation position detector that is a combination of a semiconductor magnetic sensor and a detection magnet that is attached to a rotation shaft that supports a rotor core. The semiconductor magnetic sensor outputs a signal according to the magnetic field of the detection magnet, which changes as the rotation shaft rotates. In comparison to the resolver, the rotation position detector provides a combination of (i) a semiconductor magnetic sensor which is an electronic part and (ii) a detection magnet. Further, in comparison to the resolver, which is a voluminous structural part, the rotation position detector has a smaller volume, which improves installability and motor assembly.
However, the detection accuracy of the resolver may deteriorate under the influence or disturbance of a foreign magnetic field (i.e., a disturbing magnetic field). Further, due to the structure, the resolver may easily be influenced by the disturbing magnetic field, which deteriorates detection accuracy. That is, because the resolver is equipped with a magnetic field collecting iron core with which the magnetic field/flux from a magnetic field generation part is collected), the magnetic sensor of the rotation position detector, which serves as a detecting element for detecting the magnetic field and does not include a magnetic field collecting iron core, may be easily influenced by the disturbing magnetic field, which deteriorates detection accuracy.
Since the detection magnet of the rotation position detector generates only a small magnetic field compared with a magnetic pole magnet, which is attached to the rotor core, the magnetic field leaked from the magnetic pole magnet will influence the magnetic sensor as a disturbance. In addition, the disturbance of the detection magnet is more noticeable, because, in recent years, the magnetic pole magnet is made of a rare earth permanent magnet.
As such, when the detection accuracy of the rotation position is low, an electric current supplied for a stator conductor of the rotating electric machine may have a harmonic generated therein, which may cause an uneven rotation or the like. Therefore, when the rotating electric machine uses a magnetic sensor, it is desirable for the rotating electric machine to have a configuration in which the magnetic sensor is not influenced by the magnetic field that is generated by the magnetic pole magnet of the rotor.